DESCRIPTION: (Applicant's Abstract) Little is known about the mechanisms within the spinal cord which allow some persons with spinal cord injury to recover significant function, while others do not. We propose to conduct a series of electrophysiological and behavioral measures on persons with acute spinal cord injury who are admitted to Jackson Memorial Hospital. Subjects will be studied as many as 12 times after injury, in order to accurately define the time-course of any neurologic improvement or alteration seen. Approximately 150 subjects will be enrolled over a 5 year period. Clinical strength (through manual muscle test) and muscle electrical activity (EMG) will be recorded from multiple muscles of the arms and legs for persons with injury to the cervical spine, or from the legs in persons with injury to the thoracic or thoracolumbar spine. In addition to voluntary contractions, non-invasive magnetic stimulation of the brain will be used in some subjects to cause contractions of muscles made weak by the spinal cord injury. The size of the evoked EMG response, the time at which the response occurs, and the intensity of brain stimulation needed to cause a response will be determined for each muscle, to provide objective measures of conduction in spinal cord motor tracts. Reflex responses will be measured to estimate spinal cord excitability, and magnetic resonance images of the region of damage will be obtained at 3, 12, and 24 months after injury in a subset of individuals who have recovered some voluntary movement in the legs, in order to match changes in tissue properties (e.g. edema, myelination) with clinical function. In addition to providing valuable scientific information not currently available, this project will benefit attempts to implement clinical trials of treatment interventions for spinal cord injury - trials which are now being seriously considered and for which animal studies are underway. Specifically, the information gained from the successful completion of studies proposed herein will: 1) provide some sense of a given subjects's potential for spontaneous recovery of volitional motor activity and its time-course, to help establish whether there is an optimal time post-injury to apply whatever interventions are developed; 2) contribute towards the development of objective measures for prognosis; 3) develop criteria to select the most appropriate candidates for a particular intervention; and 4) guide decisions regarding which type of intervention might be most advantageous for a certain type of injury.